Psoas Compartment Block 

Updated: Jan 10, 2018
Author: Bassem Abraham, MD; Chief Editor: Meda Raghavendra (Raghu), MD 

Overview

Background

Blockade of the lumbar plexus can be attained through an anterior approach described by Winnie[1] or through a posterior approach (psoas compartment block). The simplicity of completing the Winnie technique, well known as the 3-in-1 block, has made the technique much more popular than the posterior approach.

Controversy exists as to whether the anterior approach indeed covers the 3 target nerves: the femoral, obturator, and the lateral femoral. A meta-analysis found that more success is achieved with the obturator nerve block with the psoas compartment block when compared to the Winnie technique.[2] The obturator nerve provides innervation to the hip joint as well as the knee joint and, therefore, the degree of covering the nerve by the block results in better pain control and patient satisfaction.

Indications

Blockade of the lumbar plexus in combination with the sciatic nerve can provide anesthesia and high-quality analgesia for the whole lower extremity, with the advantage of more hemodynamic stability when compared to epidural analgesia.[3, 4, 5, 6] When a surgical block of the lower extremity is indicated, the psoas compartment block is favored over the Winnie technique. A surgical block may be considered for lower extremity amputation cases as well as orthopedic surgery cases in debilitated patients who may not tolerate the hemodynamic effects of general anesthesia.

The block may be done in conjunction with an IV opioid PCA instead of combining it with the sciatic nerve block for postoperative pain control. The use of the block is not only limited to the adult population but also extends to the pediatric population. Psoas compartment block was found to be a better technique for postoperative analgesia after hip and femoral surgery when compared to epidural block in children.[7, 8]

In a prospective single-blind study performed with 30 patients, Turker et al concluded that, when compared to epidural analgesia, lumbar plexus catheters are better tolerated for providing intraoperative and postoperative analgesia to hip fracture patients and for partial hip replacement surgery patients.[9] When combined with T12-L1 and sciatic nerve block, psoas compartment block can also be used in high-risk patients as the anesthetic technique for femoropopliteal bypass surgery.[10]

Contraindications

See the list below:

  • Patient’s refusal or lack of understanding of the benefits and adverse effects of the procedure

  • Anticoagulated and coagulopathy patients: Psoas compartment block is a paravertebral block. Although considered as an alternative for an epidural block in anticoagulated patients, this is no longer the case. The same American Society of Anesthesiology’s anticoagulation guidelines apply to paravertebral blocks.[11]

  • Localized and systemic infection

Anatomy

The lumbar plexus is formed within the substance of the psoas major muscle by the anterior rami of spinal nerves L1 through L4 and some fibers from T12. These nerve roots enter the psoas muscle within a confined compartment; they then divide into anterior divisions (forming the lumbar plexus) and posterior divisions.

The plexus is about 3 cm anterior to the plane of the lumbar transverse process. Under ultrasound guidance, it appears as a hyperechoic structure that lies within the hypoechoic psoas major muscle (see the image below). The plexus is responsible for the innervation of lower abdomen and anterior and medial portion of the lower extremities. The branches of the lumbar plexus include the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous nerve, femoral nerve, and the obturator nerve.[12]

Ultrasound guided View of the Transverse process. Ultrasound guided View of the Transverse process. The probe is placed parallel to the spinous processes S. sacrum, TP. Transverse process, LP. Lumbar Plexus

The block is approached at the L4 level in a sagittal plane that corresponds to the lateral end of the lumbar L4 transverse process. Completing the block at this level decreases the probability of puncturing the ipsilateral kidney.

 

Periprocedural Care

Equipment

See the list below:

  • A low-frequency curved array ultrasound probe (2-5 mHz)

  • Chlorhexidine for area skin sterilization

  • 25-gauge needle and lidocaine 1% for skin topicalization

  • Sterile gloves

  • Pack of sterile towels

  • Sterile ultrasound probe cover

  • Stimulating active tip catheter, insulated 4-inch Toughy needle, and loss of resistance syringe (if a catheter will be inserted)

  • Neurostimulator

  • Short bevel 10-15 cm insulated needle

  • Ropivacaine 0.5% or bupivacaine 0.25%, 30-mL volume

Patient Preparation

Positioning

The patient is positioned in a lateral decubitus position with a forward tilt and hip flexion. The full lower extremity should be exposed to watch for muscle contraction, especially if neurostimulation will also be used together with ultrasound guidance or with the loss of resistance technique.

 

Technique

Approach

The patient is positioned in a lateral decubitus position with a forward tilt and hip flexion (see image below). The full lower extremity should be exposed to watch for muscle contraction, especially if neurostimulation will also be used together with ultrasound guidance or with the loss of resistance technique. Monitoring of blood pressure, pulse oximetry, and EKG with 2 L of supplemental oxygen are recommended.

Patient in a lateral decubitus position. Patient in a lateral decubitus position.

With the traditional neurostimulation and loss of resistance technique, a line is drawn connecting the iliac crests, which coincide with the L4-L5 level. Another perpendicular parasagittal line parallel to the axial spine line is drawn, and this roughly coincides with the tips of the lumbar transverse processes. The intersection of the parasagittal longitudinal marking with the line marking the 2 iliac crests coincides with the area over the tip of the L4 transverse process. The area of interest is then sterilized, covered, and draped in the standard sterile fashion, and the skin is then topicalized with a 25-gauge needle.

A short bevel insulated needle is then advanced till it contacts the transverse process. It should then be directed cephalad or caudad to bypass the transverse process and advanced for 2-3 cm. Stimulation of the lumbar plexus results in a contraction of the quadriceps muscle as well as the adductor muscle group. The local anesthetic is then injected.

A catheter may be placed and advanced 3-5 cm past the needle tip. If a stimulating catheter will be placed, stimulation of the catheter should be performed before injection of the local anesthetic. A Toughy needle and loss of resistance technique may be used instead as described above. Upon entering the psoas compartment, a loss of resistance occurs. This technique can be combined with an active tip-stimulating catheter for confirmation of placement.

In a prospective, observer-blinded pilot study of 30 patients comparing the nerve stimulation with the loss of resistance technique, Danelli et al[13] concluded that the 2 techniques are comparable in terms of local anesthetic consumption, morphine requirements, and pain scores; however, the nerve stimulation allowed faster readiness for surgery than the loss of resistance technique.

In the ultrasound-guided approach, a curvilinear low-frequency probe is placed longitudinally over the sacrum, and then the scanning should advance in a cranial direction. The first spinous process seen is most likely that of the fifth lumbar vertebrae; proximal to it will be the L4/L5 intervertebral space and then the fourth lumbar vertebrae spinous process. The probe is then rotated to scan transversely at that level. The articular processes appear as hypoechoic structures bilaterally. The corresponding transverse process is seen lateral to the articular process.

The probe can then be moved more laterally until the tip of the transverse process is seen. A needle can then be advanced from medial to lateral towards a point just distal to the tip of the transverse process. The needle trajectory should then be adjusted to approach the plexus, which is located about 3 cm anterior to this point. The authors advocate using a stimulating needle in combination with the ultrasound guidance for confirmation of the placement because it is not always easy to visualize the hyperechoic plexus described above.

In a prospective observational study done on 53 patients, Ilfeld et al[14] concluded that prepuncture ultrasound imaging accurately predicts transverse process depth to within 1 cm if the lumbar plexus is estimated to be within 3 cm of the transverse process. Ultrasound allows prediction of the maximal lumbar plexus depth to within 1 cm.[14] Not advancing the needle from a lateral to a medial direction is important because this may result in inadvertent spinal canal injection. During the early stages of the scan, scanning laterally to visualize the lower pole of the kidney is recommended. This increases the safety of the procedure and decrease the risk for renal injury.

Complications

See the list below:

  • Inadvertent spinal or epidural injection

  • Spread of the injectate toward the epidural space

  • Injury to the kidney

  • Bleeding

  • Epidural or para-vertebral hematoma

Conclusion

Ultrasound guidance for the psoas compartment lumbar plexus block makes the approach safer and less time consuming. The technique offers an alternative to the 3-in-1 block and should be highly considered if proximal coverage of the obturator nerve and lateral cutaneous nerves are indicated. The technique may also be considered in patients with distorted anatomy that impedes the completion of the 3-in-1 approach, especially with vascular femoral procedures and in cancer patients who had inguinal area exploration and dissection.

 

Medication

Medication Summary

The goals of pharmacotherapy are to provide surgical and postoperative analgesia, reduce morbidity and prevent complications.

Local Anesthetics, Amides

Class Summary

Local anesthetics are used for local pain relief.

Lidocaine (Xylocaine)

Lidocaine inhibits depolarization of type-C sensory neurons by blocking sodium channels. Topical 1% lidocaine (Xylocaine) is a commonly used anesthetic.

Ropivacaine (Naropin)

Ropivacaine decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses. This agent is an option for longer postoperative analgesia. The onset will be delayed from 5 min to about 20 min.

Bupivacaine and epinephrine (Marcaine, Vivacaine, Sensorcaine)

Bupivacaine 0.25% with or without epinephrine may be used. It decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses.

Other Drug Category

Class Summary

These agents inhibit growth of gram-positive and gram-negative bacteria.

Chlorhexidine gluconate (PerioGard, Peridex, Hibiclens, Avagard)

Chlorhexidine binds to negatively charged bacterial cell walls and extramicrobial complexes. It has bacteriostatic and bactericidal effects.